1. Field of the Invention
This invention relates to a sulfonated aniline-type copolymer and a process for the production thereof. More particularly, this invention provides an electric conductive polymer which is soluble in water or an alcoholic solvent.
The obtained polymer solution may be applied to various kinds of antistatic treatment using a simple method such as a coating, spray or dipping method.
2. Description of the Related Art
A proton-doped polyaniline is well known as an electric conductive polymer, however, the proton-doped aniline has a drawback in the molding step or the processing step owing to the insolubility of almost all solvents.
Under these circumstances, a water soluble sulfonated polyaniline that reveals electric conductivity without the addition of a dopant, as well as a process for the production thereof have been proposed.
Examples of the process for the production of the sulfonated polyaniline are as follows: a process for the production of a sulfonated polyaniline by electrochemically polymerizing an aniline and an m-aminobenzene sulfonic acid (Nihon Kagakukaishi, 1985, 1124; Japanese Unexamined Patent Publication No. 2-166165); a process for the production of a sulfonated polyaniline by chemically polymerizing an aniline and o- or m-aminobenzene sulfonic acid (Japanese Unexamined Patent Publication No. 1-301714 corresponding to U.S. Pat. No. 4,956,441); a method of sulfonating an emeraldine-type polymer (polyaniline) obtained by polymerizing chemically or electrochemically using a conc. sulfuric acid (Japanese Unexamined Patent Publication No. 58-210902 corresponding to EP-96319A); a method of sulfonating using anhydrous sulfuric acid and a triethyl phosphate complex (Japanese Unexamined Patent Publication No. 61-197633) and a method of sulfonating using a fuming sulfuric acid (J. Am. Chem. Soc., 1991, 113, 2665-2671; J. Am. Chem. Soc., 1990, 112, 2800, WO91-06887) and the like.
The first mentioned process (Nihon Kagaku kaishi, 1985, 1124; Japanese Unexamined Patent Publication No. 2-166165) had drawbacks in that the isolating process for the product was complicated because of the formation of the product on the electrode, and because a large number of products were difficult to synthesize.
The present inventors attempted to follow the second-mentioned process (Japanese Unexamined Patent Publication No. 1-301714). Namely, the present inventors carried out the process for the polymerization of aniline and m-aminobenzene sulfonic acid using an ammonium peroxodisulfate, as is described in said publication. It was then found that only about one sulfonic acid group per five repeating units was introduced in the obtained product.
Furthermore, the present inventors carried out the process for sulfonating a polyaniline using a fuming sulfuric acid as was described in Japanese Unexamined Patent Publication No. 61-197633 mentioned above. It was also found that only about one sulfonic acid group per five repeating units was introduced in the obtained product as described in the publication, page 7, because the reaction proceeded in the dispersion state owing to insufficient solubility of the polyaniline with regard to the sulfonating solvent, and there was a problem in that the obtained sulfonated polyanilines, including a small amount of the sulfuric acid group therein, were found to be deficient with regard to electric conductivity and solubility.
Next, when sulfonating a polyaniline with a fuming sulfuric acid, about one sulfonic acid is introduced into two repeating units (J. Am. Chem. Soc., 1991, 113, PP2665-2671; J. Am. Chem. Soc., 1990, 112, 2800).
However, when fully sulfonating polyaniline by means of the above process, it is necessary to add an aniline to an amount of the fuming sulfuric acid, because of insufficient solubility of a polyaniline with regard to the fuming sulfuric acid.
Furthermore, when the amount of fuming sulfuric acid is insufficient, a part of the polyaniline solidifies and is not sulfonated thereon.
Therefore, it is necessary to determine a method of introducing much more sulfonic acid groups into the aromatic ring in order to reveal the electric conductivity and improve solubility without the addition of a dopant to a polymer.
Also, when considering the molding properties, such as a film forming property using a coating and in particular when considering the probability of coating the polymer on both a hydrophic and a hydrophobic substrate material, the obtained polymer should preferably enjoy good solubility with regard to water and alcohol and the like.
However, the prior sulfonated polyaniline has good solubility with regard to water, but has low solubility with regard to alcoholic solvents.